Hi there
I've made this guide because I have seen a lot of guides that aren't that good, and I wanted to help others to be better as Darius.
I am playing Darius since the first day he was released, for me he is the most fun-to-play champion, but also strong as hell. If you build him well, you will never loose your lane .

Pros
True damage ultimate.
Extremely high damage even if you build him as a tank .
Even he got nerfed a lot is still OP.
Low mana costs.
Can easily fight against 2 enemy champions.
Strong jungler/counterjungler
Can't be countered.

Cons
He has no escaping skills, except the summoner spells.
Very focused, even if is tanky.
Very weak against ranged champions.( or at least until level 3 )

These are very very important because he has no escaping skills.
The best choice is Flash and Ignite.
You can also take Exhaust and Flash or Exhaust and Ghost.

This is the most important, you should have 100 creeps at 10 minutes or so. Never stop farming, do it continously and if you get ganked too often just hug your turret and get as much as you can.
Remember: 2 creep waves are worth like a kill.

Darius is an aggressive champion, so never stop poking the enemy top laner and fight him when you have more creeps to help you. Between level 1 and 8 the creeps are doing a lot of damage so use them in your advantage. NEVER ever fight the enemy top laner when he has too much minions because they are deadly (nerf minions not Irelia).
Until level 6 just farm and harass/poke your enemy and when you are 6 wait for the occasion to pull him and pwn his ***.
When your enemy is garen/teemo/yorick ( your worst enemies ) play extremely aggressive, only after level 2-3. When you have your Apprehend start pulling them as much as you can. Never run away from them because their cooldowns are over 5 seconds and your hemmorhage has no cooldown, so keep attacking them until they get into the turret's range. Remember this: Hunt him until you can Decimate him because 5stacks of hemmorhage are adding a nice amount of damage.

This is a guide for ranked games so I will tell you everything you need to know.

Early game

- First of all you need to have a decent creep score. It's better to keep poking your enemy but in the same time do last hits . As Phreak said in the champion spotlight stay between your minions and the enemy's minions. Look for nearby fights and focus the most squishy champion, like their lowest health champion. (still available in midgame)

Midgame

- You shouldn't be top lane anymore, your enemy's turret should be already destroyed so go and help you teammates. Gank mid/bot and try to countergank. If your team is doing well ask your jungler to help with the Dragon.

Lategame

Here a single one mistake can ruin the entire game, so try not to make mistakes.
Even you aren't a support you should have 1-2 wards with you, if you have space in your inventory. Place some wards in your jungle if your support doesn't to prevent the baitings or traps .
When you don't see the enemies on the map there are 4 possibilities where they could be:
- In their jungle
- Taking Baron/ Dragon
- Preparing a trap
- Fapping/Throwing a party in base

DO NOT have walks farming when you don't have vision in your jungler because you can destroy a game. Just stay in the base and farm.

If your team is wining:
Don't get greedy and try to make traps, like hiding in a bush where they haven't got vision and wait for somebody, after you caught one of them the game is 5vs4, for about 1 minute. Profit.

Teamfights
Here you have to respect 3 rules:
- Do not go in the fight alone.
- Protect your AD carry and your AP caster.
- Focus the enemy AD carry or/and the AP caster (only if your team has somebody to protect your AD carry/AP caster.)

I am using 21/9/0 on Darius because in-game I build him as an offtank(70-30). I don't want 9/21/0 masteries for Darius because they are not giving you a very strong early game. In my oppinion you need a strong early game to take a few kills and if you got 3 kills nobody can stop you to get more.
Some preffer the 9/21/0 masteries but they don't build him enought tanky.

Let me tell you something. I lost a very high amount of elo because of PRO players that helped their teammates. Like this:
They went farming on lanes and in jungle at 40+ minutes and they got killed - the game was lost.

So, please remember this. I mentioned it in the "ranked play" chapter aswell. Do not go farming when you are in lategame, IT IS TOO DANGEROUS!
All the time stick together with your team, defend your carries and communicate as much as you can with them in fights by pinging. Always discuss your strategy. E.G. "we go both from behind and kill the ad and the ap and the rest bait the dps"
The communication should be like this. And of course, don't blame them for mistakes. Try to make them not to do it anymore ..

Here I will tell you in what order you should use your abilities. It is not that important but it's effective .
On the lane you just have to poke the with your Decimate.
But when you fight you do this:

1. Enemy initiation: Basic attack -> Crippling Strike -> basic attack-> Decimate -> a few basic attacks -> Crippling Strike -> you can pull your target back now -> Crippling Strike -> Decimate -> Noxian Guillotine.
W -> attack -> Q -> attacks -> W -> E -> W -> Q -> R
This combo should destroy somebody.


2. Your initiation: Apprehend -> Crippling Strike -> basic attack -> Decimate -> basic attack -> Crippling Strike -> Decimate -> Noxian Guillotine

E -> W -> attack -> Q -> attack -> W -> Q -> R

If your target is lower on health you can execute him faster. This combo is for high health targets.

Darius is a strong top laner and he can jungle as well .
Here is the jungle route I use:
Blue - Wight(smite) - Wolves - Wraiths(can be skipped) - red - gank

If the enemy jungler takes the blue buff first u can do this:
Wolves - Blue and go to his red buff waiting for him. You can get first blood on him easily . Just hide somewhere not to be seen and the red golem will take his health down .

Here you can choose a build that you like or you need.

Against high AP team

Against high AD team

REMEMBER! A really good Darius player has NO counters!
The strenght rating is between 1-10, you should not pick Darius for who is over 9.(I'll keep adding more champions)
This guy is Darius' toy
Difficulty = 3

She is a quite strong, and if well played she can beat Darius.
Difficulty = 5.5

Some say she is op, well.. against Darius is not
Difficulty = 4

Irelia is so cute ^^ but also very strong. At level 1 she can beat you for sure but if you got a kill and she didn't you won your lane. Just wait for her to make a mistake or call for your jungler and that's all.
Difficulty = 5

Easy lane, you counter him very hard thanks to your Crippling Strike and Apprehend. Remember, Ghost counters Ghost.
Difficulty = 4

Well yea, here is the famous Teemo. The most say he is Darius' counter, I can say that he is not. He can poke you, true.. but if you can avoid him until level 3 he is dead. You just have to pull him and **** him up.
Difficulty = 5

Ok, here is somebody who really can pwn Darius. Just play safe and wait for your jungler to help. He is Darius' perfect counter. If you play aggressive he can knock you back after you pull him and if you play safe he will keep poking you. There is a good way to be able to beat him. Keep playing aggressive even you can't kill him, he will not attack you anymore if you jump on him after he hits you. One more thing is this: wait for him to change his weapon, from hammer to ranged and attack fast. His cooldown is 6 seconds so you have enought time to pull+kill him.
Difficulty= 8

Eh, this Yorick ... I hate him so much. You should be afraid of him.. If you want to win just let him dive or pwn him with your jungler. If he is not going tanky(armor) you can kill him fast, but if he does don't fight with him.
Difficulty = 10

I don't like her, she can poke you a lot and her ultimate counters yours. Just try to pull her as much as possible and she will be afraid of you. When she is trying to poke you just be aggressive but have an eye on the minimap, the jungler can win the top lane .
Difficulty = 8

Talon is a bruiser, and he has 0 tankiness so you don't have to worry about him, but remember to get a Vision Ward at level 6 because of his ultimate. When he gets close pull him to you with Apprehend or just poke him with Decimate.
Difficulty = 2

Garen is a hard counter for Darius. I don't think Garen is Darius' counter.If you can play smart, avoid his Q and then counter attack with the Crippling Strike -> Decimate combo. This will poke him very hard and if you don't let him to regain his health just keep poking.
Difficulty = 5

Vladimir is weak against Darius, he just has a strong poke. An early gank will help you to own him 1vs1 easily. Just play aggressive and be very careful to the jungler.
Difficulty = 4

He is the weakest champion against Darius. When he pokes you just pull him back and finish him, he won't do the same mistake ever..
Difficulty = 1

I haven't seen a poppy player for months, she is a very unpopular champion. But anyways, if you see a poppy in the enemy team, you go against her because you will win for sure. She just can't kill a Darius.
Diffuculty = 3

All you gotta do is hit-move-hit-move-hit-move. He can't beat you like that.
Difficulty = 6

Elise... that's not good. Darius is weak against her because she can poke extremely hard and you can't even farm when she is there.I don't recommend picking Darius against her.
Difficulty = 8
Master Yi is not a strong champion in early game, but Darius is. So you get fed in early game, still own him in late game.
Difficulty = 5

Shen is a strong top laner so you should play very good and smart. He is gaining health while that blade is on the top of your head so remember that. Just run and when he turns back counter attack with Q W and then retreat.
Difficulty = 6

Jax is a very strong top laner and you need to play carefuly. Try to poke him with Decimate and you can kill him when he is low on health.
Difficulty = 7

He is you, so you know what he can do. Poke him with Decimate and try not to give him the first kill cuz' who takes the first kill will domiate the lane.
Difficulty = Depends on the player's skill

Gangplank can poke you easily so you have to be careful.. You wont be able to fight with him with low health. Here is what to do: When he is getting close to poke you, pull him and do same. Like this you will win against him.
Difficulty = 7

Here in another very strong top laner, his poke power is very high ( from where does he have so many spears?) When he is poking you do pull him, but not always because if your health is low he will kill you. Play smart and you'll win.
Difficulty = 7

Zed is very weak against Darius because he is a bruiser and his health is low, very fragile. Build Darius well and you win top( I recommend my build:D )
Difficulty = 3

He is extremely strong against any type of champions but if you know how to play against him you can win the fights. First of all you have to know that his burst is extremely strong (300-500dmg at lvl 3) so dont fight without some armor. You could rush the Ninja Tabi
Difficulty = 7

You can easily kill her but dont underestimate her because her stealth can pwn you easily, so be careful when she is getting invisible. To be 100% sure u pwn her buy a Vision Ward.
Difficulty = 3

He is a strong guy, he has everything.. long range poke, high burst damage, tankyness, true damage skill and other strong abilities. Once you killed him he can't stop you anymore. When u just arrived on top dont play passively because he will poke and take you down. Play aggressive and get fb.
Difficulty = 5

Yea... this little yordle.. I hate him, everyone does for sure. Once he is level 3 you can't really stop him .. He will keep poking you until he takes you down, he is using energy so he has no mana problems. Just wait for an opportunity to pull him to you and take him down. Remember to stay behind your minions !
Difficulty = 8-9

This guy is gonna rape you so hard, I mean.. SO HARD! Just sit like a good boy peacefully and farm those creeps. Eventually ask for your jungler to gank but before 6, after 6 he can get a double kill if he is farmed up enough.
Difficulty = 7 -8
Go on him when you are sure you can get him. His slow is very strong so keep you Apprehend until he wants to run.
Difficulty = 3

His passive is countered by your ultimate so after level 6 has no chance. Just farm until lvl 6 and then own him.
Difficulty = 5